The present invention relates to closure devices, their manufacture and use to occlude a defect in a tissue or muscle of a animal, such as a human being, or a defect in a wall of a structure, such as a container or filter. More specifically, the present invention relates to a self-expanding closure device having a membrane that is supported by a structure having elastic properties, which is capable of being compacted and inserted through a defect, and thereafter returned to an enlarged configuration to cover or seal the defect.
A wall defect is generally a hole in the wall of the tissue of an animal, such as humans, or a hole in the wall of a container, tank, bag filter, or planar filter, tent, inflatable device, etc. In muscles or tissues of animals, repairs have been accomplished by inserting an occlusion or septal closure device into the aperture or defect. Such devices include those taught by U.S. Pat. Nos. 5,334,217 to Das and 5,108,420 to Marks.
The Das patent describes a septal defect closure device, its use and method of assembly, where individual disks of a thin flexible material are supported by a super-elastic material and are used to occlude a wall defect. The disks are conjointly attached to one another at the center of the disk. The thin flexible material used in the Das patent can include nylon, polyester, polypropylene and polytetrafluoroethylene (PTFE) polymers. The super-elastic material is a NiTi alloy (or xe2x80x9cnitinolxe2x80x9d.)
The super-elastic material of the Das patent is formed into a frame having several legs and can assume geometrical configurations such as triangles, hexagons, circles, and stars. A membrane is wrapped around the legs of the frame. The loops between adjacent legs bias the legs outwardly, to form a concave membrane surface, which is maintained in a highly tensioned fashion.
The Marks patent describes an occlusion device that can be transported via a catheter in a compressed state. Once through an aperture to be occluded, the device is released and wires supporting two membranes are positioned on each side of the aperture. A domed or umbrella shaped configuration is formed and the support wires urge the membranes towards one another and the wall where the aperture is located.
These prior devices have numerous drawbacks. The support frames of the Das patent include resilient wire loops where leg ends of the frame meet and are attached to one another. The loops generally extend beyond the periphery of the membrane and can irritate or damage adjacent muscle or tissue.
Similarly, the exposed wires of the Marks device act as an irritant to tissue or muscle adjacent the aperture or septum. Here the bare sharp ends of the wire structure can further cause tissue erosion.
The Das and Marks patent devices use a membrane of conventional thickness that when folded over a wire add undesired thickness to the device. Additionally, the patents rely on peripheral membrane support which leaves the central occlusion covering portion of the membrane vulnerable.
In the Das patent design, each leg is provided with a bend at the middle of its length. This bend may tend to fold the device when the frame is sitting against a very flexible tissue and the membrane is pressurized by the blood. This may be the potential mechanism of failure as reported in Agarwal, S. K., Ghosh, P. K. and Mittal, P. K., xe2x80x9cFailure of Devices Used for Closure of Atrial Septal Defects: Mechanisms and Management,xe2x80x9d The Journal of Thoracic and Cardiovascular Surgery, Vol. 112, No. 1, 1996.
Finally, it is believed that none of the previously available devices have provided a sufficiently small enough insertion diameter and/or collapsed flexibility. This limitation has restricted the utility and ease of use of such devices.
Thus, in view of the above, it is desirable to provide a closure device that eliminates or significantly minimizes the traumatizing effect of existing closure devices. Further, it is desirable to provide such a device to be stable under physiological loading conditions when situated against the anatomical tissue structure. It is additionally desirable to provide a defect closure device that is collapsible or compressible so that it may fit into a 9F (9 French), preferably 5F or 4F or smaller catheter for deployment in a defect.
These drawbacks and disadvantages of the prior devices have been addressed and overcome by the inventions described in the two co-pending patent applications. These prior inventive devices employ unique nitinol frames combined with thin expanded PTFE membranes to create defect closure devices that function better than any previous defect closure devices. Of particular benefit of these devices is the fact that they are capable of being compacted into very small delivery tools and then deploy to fully operational diameters. Additionally, unlike some previous defect closure devices, these inventive devices provide excellent protection of tissue from damage by the frame, which is protected under the expanded PTFE cover. Further, these inventive devices also are capable of being relatively easily withdrawn remotely from the defect site in the case they need to be retrieved.
Despite the excellent properties of the defect closure devices disclosed in the parent applications, on-going development work has revealed that further improvements may be possible on these devices. First, it has been discovered that with devices with helical frames the device must be carefully deployed to assure that the helical frame initially starts to expand with the correct spiral. If the helix starts unwrapping in the wrong direction, the operator must withdraw the device back into the delivery tool and attempt deployment a second time to assure that the device expands correctly. Accordingly, a frame which consistently deploys with the correct bias in the helical frame is believed desirable.
Second, the use of the parent devices within tortuous anatomy generally requires the use of separate guidewire catheters or similar devices to help negotiate the device delivery apparatus to the deployment site. This requires both the use of additional equipment and often taxes space limitations at a surgical site. Thus, it is further believed desirable to incorporate a simpler and more compact system that can assist in negotiating the deployment apparatus to the defect site.
The present invention provides significant improvements to deployment and use of the self-expanding defect closure device described in the co-pending parent applications. The defect closure device of the present invention comprises a helical shape periphery supporting a membrane. The helical shape periphery is formed from an elastic wire. Specific improvements have been made to the elastic wire frame and the delivery apparatus to assure consistent correct delivery of the device at the operative site. Additionally, the deployment apparatus has been modified to aid in the negotiation of the device to the site of deployment.
Specifically, the wire frame now includes at least one eyelet having a non-circular or xe2x80x9casymmetricxe2x80x9d shape. A guiding mandrel is similarly shaped to have a complimentary non-circular or asymmetric shape which allows the eyelet to slide linearly along the mandrel. The asymmetric shapes of the wire eyelet and the guiding mandrel prevent rotation of the eyelet relative to the mandrel. This anti-rotation feature of the present invention provides a bias or constraint to the formed elastic support, particularly for a helix shaped support. Without this applied bias, a helical wire might assume various deployed shapes. The addition of the bias means of the present invention insures a consistent deployed state or configuration.
Additionally, to deliver and place a septal defect closure device intravenously, the delivery catheter often must be guided through a tortuous path. It is thus another aspect of the present invention to provide a self-articulating catheter tip which facilitates and enhances the ease of delivery. To this end, the catheter is provided with a hooked end adapted to assist in guiding the catheter tube through passageways in a body, much in the same way that a guidewire catheter can be xe2x80x9csnakedxe2x80x9d through tortuous anatomy using its hooked end to xe2x80x9csteerxe2x80x9d the guidewire into place.
In the present invention, the hooked tip is integrally incorporated into the deployment apparatus to assist in steering the deployment apparatus to the deployment site. Once in place, however, the deployment apparatus is adapted to eliminate the hooked tip to provide accurate defect closure device placement. This is accomplished by providing a self-articulating catheter tip that can be bent to a variety of angles by advancing or retracting the closure device from the proximal end of the delivery catheter. In other words, as the defect closure device is advanced through the tip of the catheter, the tip will straighten out to provide linear deployment of the defect closure device. Thus, the catheter tip is adapted to assume at least two different positions, an angular or bent guiding position and a straightened device deployment position. The catheter tip actuates from the guiding position to the device deployment position when the defect closure device is moved through the distal tip of the catheter. To accomplish this, the catheter tube comprises a flexible material adapted both to maintain a bent orientation while being negotiated into position and to flex so as to straighten the hooked end when a device is deployed through the tube.
These and other aspects and advantages will become more apparent when considered with the following detailed description, drawings and appended claims.